This invention relates to stuffer box crimping of yarn, and more particularly, it relates to a method and apparatus for controlling crimp.
Stuffer box crimpers are well known and have been widely employed for crimping filament strands, including for example, yarns, tows and threads.
In the case of tow, formed of several ropes of yarn, crimp level is controlled by the amount of force applied to the tow band by a single hinged gate associated with the outlet of the crimping chamber. A problem may arise because the thickness of the tow band entering the crimper varies across the width of the band due to interactions between the ropes which make up the tow.
The two edges of the tow band experience the greatest variations due to contact with guides employed to position the tow band ahead of the crimper. While one edge may be consistently thicker than the other, a more common occurrence is the periodic thickening of one edge with a simultaneous thinning of the opposite edge. Either of these conditions results in poor crimp uniformity across the tow band width. In severe cases operability (crimper jams) becomes a major problem. This occurs when the thick edge carries most of the gate force causing the thin edge to become slack.